P1106: CLINICAL OUTCOME OF PATIENTS WITH LOCALIZED PRIMARY GASTRIC MUCOSA-ASSOCIATED LYMPHOID TISSUE LYMPHOMA: LONG-TERM FOLLOW-UP RESULTS FROM A SINGLE-INSTITUTION OBSERVATIONAL STUDY.
Authors: Kei Hirano, Kikuaki Yoshida, Norihito Inoue, Naoko Tsuyama, Yukako Teramoto, Mitsuhito Hirano, Mikako Tanba, Nobuhiko Yamauchi, Yuko Shirouchi, Yuko Ishihara, Hiroaki Asai, Yuko Mishima, Senzo Taguchi, Toshiaki Hirasawa, Kengo Takeuchi, Dai Maruyama
Journal: HemaSphere (2023)

Topic: 18. Indolent and mantle-cell non-Hodgkin lymphoma - Clinical Background: The natural history of localized primary gastric mucosa-associated lymphoid tissue (PG-MALT) lymphoma has been reported to follow an indolent course. The eradication of helicobacter pylori (HP) has been established as the initial treatment for HP-positive patients (pts). However, several clinical questions including optimal treatment strategy (especially non-responders to HP eradication and HP-negative pts), incidence of histologic transformation (HT), and long-term outcome remain unclear. Aims: The aims of the present study were to clarify the clinical outcome in long-term follow-up of pts with localized PG-MALT lymphoma. Methods: We retrospectively analyzed pts who were initially diagnosed as localized PG-MALT lymphoma and managed in our institution between 2005 and 2021. Event-free survival (EFS) was defined as the time from diagnosis to progression, relapse, HT, or death. Overall survival (OS) was defined as the time from diagnosis to death. Time to next treatment (TNT) after HP eradication therapy was defined as the time from HP eradication therapy to the initiation of next treatment. Results: We identified 144 pts consisting of 140 stage IE and four stage IIE (according to the Lugano 2014 Classification) pts. The median age was 58 years (range, 37-85). At initial diagnosis, 46 pts (32％) were HP-positive, 97 pts (67%) were HP-negative, and one pt was unknown. t(11;18)/API2-MALT1 was positive in 29 of 93 examined pts (31%). As the initial treatment, 85 pts (59%) (44 HP-positive and 41 HP-negative) received HP eradication therapy; 52 pts (36%), including 51 HP-negative pts, were treated with RT; four pts underwent surgical resection; and three pts were managed with watchful waiting. Among 85 pts who received HP eradication therapy, 30 pts (35%) achieved complete response (CR) by biopsy including 24/44 HP-positive pts (%CR, 55%) and 6/41 HP-negative pts (%CR, 15%). Eight pts achieved CR more than 180 days after HP eradication therapy. In 15 t(11;18)/API2-MALT1-positive pts who received HP eradication therapy, none achieved CR after HP eradication. Among 55 non-CR pts after HP eradication therapy, 49 pts (89%) received RT as the second-line treatment. The median TNT after HP eradication therapy was 381 days (range, 50-6350). The 2-year TNT after HP eradication therapy was 35.3% (95%CI, 24.9-45.9%), and the events that required next treatment after 2 years were rare. The median follow-up period was 5.2 years (range, 0.19-17.5 years). The 5- and 10- year EFS were 88.7% (95%CI, 81.0-93.4%) and 81.6% (95%CI, 69.4-89.3%), respectively (Fig 1A). The 5- and 10- year OS were 96.1% (95%CI, 89.7-98.6%) and 93.4% (95%CI, 82.8-97.5%), respectively (Fig 1B). HT occurred in only two pts (1.4%) after HP eradication therapy; both of whom had gastric lesions. Five pts died during the follow-up period. The causes of death were other malignancies in four pts and pneumonia in one pt. There were no deaths due to PG-MALT lymphoma. In total, 103 pts received RT during their entire treatment period, and 97 pts (94%) achieved CR. Late onset adverse events in pts treated with RT consisted of gastric cancer (four pts), and vertebral fracture, duodenal ulcer, cholangitis, and chronic kidney disease (in one pt each). Summary/Conclusion Our findings suggest that localized PG-MALT lymphoma had favorable prognosis as no pts died with PG-MALT lymphoma and HT was rarely observed. HP eradication indicated a possible benefit also for HP-negative other than t(11;18)/API2-MALT1-positive pts. FigureKeywords: Helicobacter pylori, Radiotherapy, Gastric MALT lymphoma, Indolent lymphoma